Parallel operation of interrupting means



Aug. 24, 1943.

H. J., BROW N PARALLEL OPERATION OF INTERRUPTING MEANS Filed Jan. 3l, 1942 ZNVENTOR.

Patented Aug. 24, 1943 UNITED STATES PATENTv OFFICE PARALLEL OPERATION F INTEBBUPTING MEANS 19 Claims.

My invention relates in general to circuit interrupting systems and more particularly to a circuit interrupting system having a circuit interrupting device therefor with at least two parallel sets of interrupting meanssubstantially simultaneously operated for jointly supplying a current through a plurality of parallel interrupting paths to the electrical system. This application relates to the subject matter of my Patent No. 2,286,842 and my pending applications Serial Nos. 429,074, 429,076 and 429,077.

In the design of an interrupting device for a load circuit, substantially no difficulty is encountered in building an interrupting device that is immune to mechanical wear on the contact points. The impacts on closing and the wear due to rubbing can be so reduced that the device will operate indenitely, if at the same time, the stressed parts are properly strain-relieved and operated well below their indurance limit. With such an interrupting device, the problem is primarily one of reducing the eiiects of the electrical current and voltages on the contacts so that any required performance may be achieved. Experience shows that in an interrupting device where the make-and-break operating cycles run into the billions, the life and performance are strictly determined by the ability of the contact points to withstand the pitting and erosion of the electrical current flowing at the instant of the make-and-break. Notwithstanding the fact that the most resistant materials available to the engineering art are used, the interrupting device in many applications fails to meet the standards of reliability and life which are normally required. Interrupting devices with several sets of contact points in parallel have also been used in an effort to increase the life thereof, but here too the life and reliability of the contacts do not come up to expectations. The principal reason for the lack of satisfactory results lies in the character of the contacting materials when interrupting the current. Generally speaking, `the current in a contact necks down to an extremely high current density prior to separation, even though large shunting capacities and other current-diverting impedances be used. For reasonable values of current relative to the material used, the contact is subject to melting and vaporization at the nal tip, and if two or more .contacts are in parallel, the final single trailing contact is subject to the attack of this high current density. Similar destructive effects take place when the contact engagement is made, as the condenser-s necessary to operate the equipment. are then charged or discharged. One of the more noticeable effects is material transfer from one contact to the other, another is pitting and erosion, and in severe cases, there is arcing which is very destructive.

Contact pointdisintegration due to electrical current falls in two categories; namely, the disintegration resulting from making the contact and the disintegration resulting from breaking the contact. Both may be partially controlled by the proper handling of the circuit constants but it is unfortunately true that changes in the circuit which improve the performance at the break may harm the performance at the make, and vice versa. Therefore, the design of a good and eicient interrupting circuit which will give long life and reliability against breakdowns presents a dinicult problem to solve and a satisfactory circuit cannot be prescribed on the basis of a superficial examination. Furthermore, the absence of sparking is no criterion of a satisfactory circuit, as it is often true that the performance of mildly sparking contacts will be superior to dark ones. A further characteristic of contact points is that various thresholds of current exist below which material transfer and erosion do not occur at all or in small amounts.

An object of my invention is, therefore, the provision of reducing the electrical disintegration eliect below the threshcld value where material transfer and erosion de not eccur at all or in small amounts.

Another object ci my invention is to prevent the current nowing through one contact from diverting into another, as one contact is opened prior to another.

Another object ci invention to forcibly prevent the current flewing in two or more in terrupting contacts from re-establishing itself in a single final trailing contact tip during the short interval of time involved between the successive openings of the parallel contacts and to insure that the burden of interrupting the circuit is divided between the pair of parallel contacts.

Another object of my invention is the provision, in a circuit interrupter having a plurality of parallel interrupting paths, of preventing the current which is interrupted in an interrupted path incident to slight variations in the interruption of the plurality of interrupting paths from suddenly re-establishing itself in a yet uninterrupted path during the short interval of time involved between the successive interruptions of the parallel paths.

Another object of my invention is to keep the now of the interrupting current in the interrupting contacts less than that certain threshold value below which material transfer and erosion of the contacts do not occur at all or in small amounts.

In a set of parallel contacts, the current will divide between the contacts according to Ohms law. Since the contact resistance is small compared to the rest of the load circuit, which is ordinarily the case, the opening of one of two parallel contacts will not eect the total current now, and the total current will then flow through the remaining closed trailing contact. The timrequired for this diversion will be very small, perhaps less than i-6 seconds, as indicated by the residual inductance and resistance of the closed loops through the two parallel contacts. in any practical interrupter, the dierences in opening time may be a thousand times this value so the problem may be stated as one of increasing the diversion time perhaps a thousand or more times its ordinary value.

Therefore, another object of my invention is to provide for increasing the diversion time perhaps a thousand or more times its ordinary value.

Another object of my invention is the provision of the employment of a balancing inductance in combination with a current-diverting impedance to forcibly prevent the current flowing in two or more interrupting contacts from re-establishing itself in a single liinal trailing contact tip during the short interval of time involved between the successive openings of the parallel contacts and to insure that the burden of interrupting the circuit is divided between the pair of parallel contacts.

Another object of my invention is the provision of a T-connected inductance which does not increase the impedance to the ow of the load current but which developes an inductive impedance to the iiow of the current in the parallel sets of contacts to oppose the sudden reestablishment of the current of an interrupted parallel contact path during the short interval involved between the successive openings of the parallel set of contacts in the yet uninterrupted parallel paths, thereby preventing the damaging of the contacts,

Another object of my invention is the provision in a circuit interrupting device of reducing the electrical damage to the contacts during both the make and break cycles thereof.

Other objects and a fuller understanding of my invention may be had by referring to the following descriptionand claims, taken in conjunction with the accompanying drawing; in which:

Figure 1 diagrammatically illustrates a circuit interrupting system embodying the features of my invention;

Figure 2 is a modification of the circuit interrupting system shown in Figure 1;

Figure 3 is a diagrammatic illustration of a generator eld circuit embodying the features of my invention;

Figure 4 is a diagrammatic illustration of an ignition system embodying the features of my invention; and

Figures 5, 6, 7 and 8 illustrate, respectively, the different kinds of current-diverting impedances which may be employed in my circuit interrupting system.

With reference to Figure 1 of the drawing, my circuit interrupting system comprises an interrupting device illustrated generally by the reference character IB, having two sets of parallel interrupting contacts I! and i2, a T-connected balancing lnductance it, and a current-diverting impedance 25. The circuit interrupting systeml may be energized by a battery i@ or by any other suitable current source. As illustrated, each of the sets of the parallel interrupting contacts comprises a stationary contact and a movable Contact which moves relatively to the stationary contact to interrupt the circuit. The movable contact may be actuated by a contact actuating device i3 wherein the movements of the actuating device may be transmitted to the movable contact through any suitable mechanical transmitting arrangement such as illustrated diagrammatically by the dash-dot line indicated by the reference character iii. In the operation of my interrupting device it is to be understood that the actuation of the movable contact may be accomplishd by any suitable means. The movable contacts are electrically connected together by a common conductor l5 which is in turn connected to one side of the battery iii.

The balancing inductance has a winding with two ends 2i and 22 and a center tap 20 dividing the winding into two halves 26 and 2 with a half thereof included in each of the two parallel contact paths. The center tap 20 is connected to the load and the end 2i is connected to the set of contacts i2 through a conductor 2t and the other end 22 of the winding is connected to the set of contacts il through a conductor 23. The current diverting impedance 25 is connected across the conductors 23 and 20 and in shunt with the winding of the balancing inductance i9.

In operation, the load current divides substantially equally between the two sets of parallel contacts ii and l2 when the said contacts are closed. 'Ihe ilowing of the load current through the two halves 26 and 2l of the balancing winding balances out the inductive impedance of the said winding with respect to the load circuit. Consequently, I am able to achieve parallel operation of the two sets of contacts without liability of the inductance in the load circuit. The only eiect upon the load circuit will be that of any IR drop that may exist.

During the interruption of the parallel contacts, should the contacts Ii, for example, open slightly prior to the opening of the contacts i2, then the combination of the balancing winding andthe current-diverting impedance operates to prevent the current which is interrupted by the contact il from suddenly re-establishing itself in the yet uninterrupted parallel contact I2 during the short interval involved between they successive openings of the parallel set ofcontacts. The description with reference to the operation of the Joint action of the balancing winding and the current-diverting impedance during the short interval of time involved between thesuccessive openings of the contacts Il and l2 may be described with reference to the following assumption: let it be assumed that the load on the system is 1000 watts, the voltage of the battery volts, and that the resistance of the load is 10 ohms. Under this assumption when the contacts Il and l2 are both closed, ten amperes will flow through the load and ve amperes will flow through each of the contacts II and I2. Immediately upon the interruption of the contact II, the load on the system is reduced to 500 watts and immediately tries to build up to 1000 watts, in which event 10 amperes would iiow through the contact l2 but `my arrangement prevents this transfer of electrical load upon the contact I2. With 500 watts existing as the load and with the contacts II open 50 volts will exist across the load and 50 volts will also exist across the winding 21 which acts as a primary of a transformer and induces `100 volts between the two ends 2I and 22 of the balancing inductance. With 50 volts existing across the winding 21 and with 5 a-mperes flowing therethrough, the winding will appear to have an impedance of 10 ohms. With 10 ohms existing across the winding 21 which acts as a primary of a transformer, then the impedance of the current diverting impedance is preferably made 40 ohms since it is connected across both halves of the balancing winding. In other words, the impedance ratio of a transformer is equal to the square of the turns and in the instant case the secondary turns which comprise both the windings 2B and 21 is twice the number oi turns upon the winding 21 which comprises the primary winding of the balancing inductance. With 100 volts across both halves of the inductance windings 26 and 21 and with an impedance of 40 ohms in the current diverting impedance, 2.5 amperes will flow through the loop diverting circuit comprising the current-diverting impedance 25 and the two halves of the windings 26 and 21 of the balancing inductance. Under the above calculations, 250 watts will exist across the current diverting impedance 25 and 250 watts will exist in the load, makine'a total of 500 watts in the whole system during the short interval ci time that exists between the opening of the contact II and the, opening of the contact I2. Under the above assumption, 5 amperes will continue to ilow through the contact I2 and there will be no increase in the burden of the contacts I2 during the short interval of time involved between the opening of the contacts II and the contacts I2.

The reverse situation would occur should the contacts I2 open slightly prior to the opening of the contacts II and in this event the combination of the balancing inductance and the current-diverting impedance 25 would operate to prevent the current interrupted by the contacts I2 from re-establishing itself in the contacts Ii during the short interval of time involved between the opening of the contacts. The impedance of the. current-diverting impedance 25 Imay be of any value other than the ideal value explained in the above mentioned calculation but it must be remembered that as the impedance of the current-diverting impedance 25 increases beyond its ideal value then the nrst contact which opens takes a larger share of the burden and should the value of the current-diverting impedance 25 be decreased below the ideal value then the second contact to open takes the increased burden. In other words, as the impedance of the current-diverting impedance 25 approaches infinity, then the rst contact to open takes all the burden and as the impedance of the current diverting-impedance 25 approaches zero then the second contact to open takes all of the burden. By making the impedance of the current-diverting impedance 25 four times the impedance of the load an ideal situation exists to keep the current flowing through the contact which is last to open the same throughout the period involved between the successive opening of the contacts. illustrated a system which achieves parallel operation oi the contacts without the liability of inductance in the load circuit while at the same time I prevent the current which is interrupted in one of the contacts from being re-established in the other contact during the short interval of time between the successive openings of the contacts.

The current-diverting impedance 25 may comprise a resistor as shown in Figure 5, a capacitor as shown in Figure 6. the series combination of a resistor and a capacitor as shown in Figure 7, or the parallel combination of a resistor and a capacitor as shown i-n Figure 8. In the event that a resistor as shown in Figure 5 is employed, the resistance thereof is preferably made substantially four times the resistance of the load, i1 a capacitor as shown in Figure 6 is employed, the capacitance is preferably made substantially onefourth the capacitance of the capacitance of the load. Ir the load contains both resistance and capacitance in series, then the impedance arrangement as shown in Figure 7-is employed and here again the resistance is preferably made four times the resistance of the load and the capacitance is preferably made one-fourth of the capacitance of the load. If the load contains resistance and capacitance in parallel, then the arrangement shown in Figure 8 is employed in which the resistance is made preferably substantially four times the resistance of the load and the capacitance is preferably made substantially one-fourth the capacitance of the load.

In Figure 2 l show a modification of the circuit interrupting system oi Figure l in that I employ two current-diverting impedances 28 and 29 connected respectively across the interrupting contacts I2 and II. The current diverting impedances 28 and 29 may be any one of the combination shown in Figures 5 to 8, inclusive. The

1 operation of Figure 2 is substantially the same as that described for Figure l except that the current-diverting loop circuit, when the contacts I! are open, includes the balancing winding I9, the current-diverting impedance 29, the common inductor I5, the contacts I2, and the conductor 24 and when the contacts i2 are open the circuit includes the balancing winding I9, the currentdiverting impedance 28, the common conductor I 5, the contacts I2, and the conductor 23. In other words, the current which flows through the current-diverting loop circuit during the interval that the one contact is open prior to another contact ows in the opposite direction to the oW of the current for 'the load circuit. Therefore, if the same calculations are employed as set forth with reference to Figure l and with the contacts I I opening slightly prior to the contacts I2, then 2.5 amperes would iioW in the current-diverting loop circuit in opposition to the 5 amperes flowing through the contacts I2 of the load circuit With the result that the current iioWin-g through the yet uninterrupted contact I2 would b 2.5 amperes. Thereforey the current in the yet uninterrupted contacts of Figure 2 may be made less than the current which iiows through the contacts under normal operation.

In Figure 3 I show the employment of my current-interrupting systemin a generator iield regulating circuit, which comprises a generator 32 having a neld winding 33, a balancing inductance Therefore, in Figure 1 I have Y 3d, an electro-magnet 31, and a governing relay 4I. 'Ihe current through the field winding 33 is governed by the interrupting set of parallel contacts 35 and 36 having respectively in. parallel therewith the resistors 4D and 39. As illustrated diagrammatically, the contacts 35 and 36 are actuated by the electro-magnet 31 through a mechanical motion transmitting arrangement illustrated Iby the dash and dot lines 38. The electro-magnet 3l comprises two coil windings in which one of the coils is energized by current from the generator which flows through conductors 42 and 43 and in which the other coil therein is energized by current which flows through conductors it and 43. The current which ows through the coil connected to the conductors 4G and i3 is governed by the governing relay il which is in turn connected across the generator terminals. Therefore, when the relay lll closes its contact the electro-magnet 3l operates instantaneously to actuate the contacts 35 and 36.

The balancing inductance 3d operates to prevent the establishment of the current from an interrupted contact from suddenly re-establishing itself into the other contact during the interval between the successive opening of the contacts to insure a proper division of the current between the parallel contacts. The impedance of the balancing inductance 34 with respect to the current through the load circuit is cancelled out so that the only eiect of the balancing inductance in the load circuit is the IR drop existing therein. In Figure 4 I show the application of my circuit interrupting system to an ignition system which comprises a set of parallel interrupting contacts i8 and 49, a balancing inductance ill, a battery 52, an ignition coil 53 and a distributor 5%. The arrangement in Figure 4 for the ignition system is substantially the same as that shown in Figure 2 where the current diverting impedances are capacitors Which,`taken in combination with the balancing inductance, provide for opposing the sudden transfer or re-establishment of the current in an interrupted contact from suddenly re-establishing itself into a yet uninterrupted contact during the short interval of time involved between the successive openings of the contacts.

As explained in connection with the other illustrations, the balancing inductance offers substantially no impedance to the now of the load current therethrough since each half of the winding balances each others eiects out.

The capacitors and 5l of the ignition circuit in Figure 4 and the current-diverting impedances 28 and 29 in Figure 2 when used as capacitors, are each substantially one-half the capacity of what a condenser would be if it were connected across a single set of contacts. Therefore, it will be noted that the condenser effect is divided in halfs the capacitance of the two oondensers totalling what would normally be the entire capacitance. This means that the condenser energy is halved and its effect reduced upon the damage of the contacts.

summarizing, my invention includes the arrangement for preventing the current which is interrupted in an interrupted parallel contact path incident to slight variations in the breaking of the plurality of set of contact means from suddenly re-establishing itself in a yet uninterrupted paralle] Contact path during the short interval of time involved between the successive openings of the contact means to prevent the. damaging of ascuas the contacts. My invention further reduces the 'damaging to the contacts in that the condenser is divided into two parts wherein both parts when taken together make up the entire condenser, wherein the condenser energy is reduced to onehalf its value where the condenser is not divided. The reduction in the condenser energy reduces the effect of the damage to the contacts.

While I have illustrated and described my invention as having particular utility in connection with interrupting parallel contacts, it is to be understood that my invention is not limited thereto and, therefore, includes any interrupting system comprising interrupting means having a plurality of parallel interrupting paths which are substantially simultaneously interrupted for jointly interrupting the current in the electrical system.

Although I have described my invention with a certain degree of particularity, it is understood that the present disclosure has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

I claim as my invention:

1. In an electrical system including a load circuit and having a circui-t interrupting device therefor with at least two parallel sets of interrupting contacts substantially simultaneously operated for jointly supplying a current through a plurality of parallel contact paths to the load circuit; the arrangement for preventing the current which is interrupted in an interrupted parallel Contact path incident to slight variations in the breaking of the plurality of sets of contacts from suddenly re-establishing itself in a yet uninterrupted parallel contact path and increasing the burden dn the set of contacts therein during the short interval involved between the successive openings of the parallel sets of contacts, said arrangement comprising the combination of current-diverting impedance means connected in eiective electrical current-diverting relation with the parallel sets of contacts, and a balancing inductance having a winding with two ends and a center-tap dividing the said winding into two halves with -a half thereof included in each of the two parallel contact paths for developing, in series with each of the parallel sets of contacts, an inductive impedance to the flow of current therein, the inductive impedance in the yet uninterrupted parallel contact path opposing the sudden re-establishment of the current of the interrupted parallel contact path during the short interval involved between the successive openings of the parallel sets of contacts in the yet uninterrupted parallel path, thereby preventing the damaging of the contacts, the said cen-ter-tap being connected to the load circuit and the Said ends of the balancing Winding being connected respectively to the two parallel contact paths, thus forming a T-connection to balance out the inductive impedance of the said winding with respect to the load circuit.

2. In an electrical system including a load circuit and having a circuit interrupting device therefor with at least two parallel sets of interrupting contacts substantially simultaneously operated for jointly supplying a current .through a plurality of parallel contact paths to the load circuit; the arrangement for preventing the current which is interrupted in an interrupted parallel contact path incident to slight variations in the breaking of the plurality of sets of contacts from suddenly re-establishing itself in a yet uninterrupted parallel contact path and increasing the burden on the set of contacts therein during the short interval involved between the successive openings of the parallel sets of contacts, said arrangement comprising the combination oi' current-diverting impedance means connected in e!- fective electrical current-diverting relation with the parallel sets of contacts, and a balancing inductance having a winding with two ends and a center-tap dividing the said winding into two halvesA with a half thereof included in each of the parallel contact paths for developing, in series with each of the parallelsets of contacts, an inductive impedance to the ilow of current therein, the inductive impedance in the yet uninterrupted parallel contact path opposing the sudden re-establishment of the current of the interrupted parallel contact path during the short interval involved between the successive l openings of the parallel sets of contacts in the loop circuit to allow curren-t to ilow therein dur-` ing the short interval involved between successive openings of the parallel sets of contacts.

3. In an electrical system including a load circuit and having a circuit interrupting device therefor with at least two parallel sets of interrupting contacts substantially simultaneously operated for jointly supplying a current through a plurality of parallel contact paths to the load circuit; the arrangement for preventing the current which is interrupted in an interrupted parcircuit and having a circuit interrupting device allel contact path incident to slight variations in the breaking of the plurality oi' sets of contacts from suddenly re-establishing itself in a yet uninterrupted parallel contact path and increasing the burden on the set of contacts therein during the short interval involved between the successive openings of the parallel sets of contacts, said arrangement comprising the combination of current-diverting impedance means connected in efiective electrical current-diverting relation with the parallel sets of contacts, and a balancing inductance having a winding with two ends and a center-tap dividing the said winding into two halves with a half thereof included in each of the parallel Contact paths for developing, in series With each of the parallel sets of contacts, an in-v ductive impedance to the iiow of current therein, the inductive impedance in the yet uninterrupted parallel contact path opposing the 'sudden reestablishment of the current of the interrupted parallel contact path during the short interval involved between the successive openings of the parallel sets of contacts in the yet uninterrupted parallel path, thereby preventing the damaging of the contacts, the said center-tap being connected to the load circuit and the said ends of the balancing winding being connected respectively to the two parallel contact paths, thus forming a T-connection to balance out the inductive impedance of the said winding with respect to the load circuit, said balancing inductance and said current-diverting impedance therefor with at least two parallel sets of interrupting contacts substantially simultaneously operated for jointly supplying a current through a plurality of parallel contact paths to the load circuit; the arrangement for preventing the current which is interrupted in an interrupted parallel contact -path incident to slight variations in the breaking of the plurality of sets of contacts from suddenly re-establishing itself in a yet uninterrupted parallel contact path and increasing the burden on the set of contacts therein during the short interval involved between the successive openings oi.' the parallel sets of contacts, said arrangementl comprising the combination of current-diverting impedance means connected in eiective electrical current-diverting relation with the parallel sets of contacts, and a balancing inductance having a winding with two ends and a center-tap dividing the said winding into two halves with a half thereof included in each of the parallel contact paths for developing, in series with each of the parallel sets of contacts, an inductive impedance to the ilow of current therein, the inductive impedance in the yet uninterrupted parallel contact path opposing the sudden reestablishment of the current of the interrupted parallel contact path during the short interval involved between the successive openings of the parallel sets of contacts in the yet uninterrupted parallel path, thereby preventing the damaging of the contacts, the said center-tap being connected to the load circuit and the said ends of the balancing Winding being connected respectively to the two parallel contact paths, thus forming a T-connection to balance out the inductive impedance of the said winding with respect to the load circuit, said balancing inductance and said current-diverting impedance means being included in a current-diverting loop circuit to allow current to ilow therein and prevent the current which flows in the parallel path containing the uninterrupted set of contacts from substantially increasing during the short interval involved between successive openings of the parallel sets of contacts, said current-diverting impedance having a value substantially four times the value of the impedance of the load circuit.

5. In an electrical system including a load circuit and having a circuit interrupting device therefor with at least two parallel sets of interrupting contacts substantially simultaneously operated for jointly supplying a current through a plurality of parallel contact paths to the load circuit; the arrangement for preventing the current which is interrupted in an interrupted parallel contact path incident to slight variations in the breaking of the plurality of sets of contacts from suddenly re-establishing itself in a yet uninterrupted parallel contact path and increasing the burden on the set of contacts therein during the short interval involved between the successive openings of the parallel sets of contacts, said arrangement comprising the combination of current-diverting impedance means connected in effective electrical current-diverting relation with the parallel sets of contacts, and a balancing inductance having a winding with two ends and a center-tap dividing the said winding into two halves with a half thereof included in each of the two parallel contact paths for developing, in series with each of the parallel sets of contacts, an inductive impedance to the ilow of current therein, the inductive impedance in the yet uninterrupted parallel contact path opposing the sudden re-establishmentof the current of the interruptedl parallel contact path during the short interval involved between the successive openings of the parallel sets of contacts in the yet uninterrupted parallel path, thereby preventing the damaging of the contacts, the said center-tap being connected to the load circuit and the said ends of the balancing winding being connected respectively to the two parallel contact paths, thus forming a T-connection to balance out the inductive impedance of the said winding with respect to the load circuit, said current-diverting impedance means being separated into two parts of substantially the same impedance value, with one of said parts connected in shunt with the interrupting set of contacts of one parallel path and with the other of said parts connected in shunt with the interrupting set of contacts of Ithe other parallel path.

6. In an electrical system including a load circuit and having a circuit interrupting device therefor with at least, two parallel sets of 'interrupting contacts substantially simultaneously operated for jointly supplying a current through a plurality of parallel contact paths to the load circuit; the arrangement for preventing the current which is interrupted in an interrupted parallel contact path incident to slight variations in the breaking of the plurality of sets of contacts from suddenly re-establishing itself in a yet uninterrupted parallel contact path and increasing the burden on the set of contacts therein during the short interval involved between the successive openings of the parallel sets of contacts, said arrangement comprising the combination of current-diverting impedance means connected in effective electrical current-diverting relation with the parallel sets of contacts, and a balancing inductance having a winding with two ends and a center-tap dividing the said winding into two halves with a half thereof included in each of the two parallel contact paths for developing, in series with each of the parallel sets of contacts, an inductive impedance to the ow of current therein, the inductive impedance in the yet uninterrupted parallel contact path opposing the sudden re-establishment of the current of the interrupted parallel contact path during the short interval involved between the successive openings of the parallel sets of contacts in the yet uninterrupted parallel path, thereby preventing the damaging of the contacts, the said center-tap being connected to the load circuit and the said ends of the balancing winding being connected respectively to the two parallel contact paths, thus forming a T-connection to balance out the inductive impedance of the said winding with respect to the load circuit, said current-diverting impedance means comprising resistance means separated into two parts of substantially the same resistance value, with one of said parts connected in shunt with the interrupting set of contacts of Aone parallel path and with the other of said parts connected in shunt with the interrupting set of contacts of the other parallel path, the resistance of each of said parts permitting the current which ilows therein during the short interval involved between the successive openings of the parallel sets of contacts to be of substantially the same value as the current which owed through Ithe associated parallel path prior to the opening of the interrupting set of contacts therein.

7. In an electrical system including a load circuit and having a circuit interrupting device therefor with at least-'two parallel sets of interrupting contacts substantially simultaneously operated for jointly supplying a current through a plurality of parallel contact paths to the load circuit; the arrangement for preventing the current which is interrupted in an interrupted parallel contact path incident to slight variations in the breaking of the plurality of sets of contacts from suddenly :re-establishing itself in a yet uninterrupted parallel contact path and increasing the burden on the set of contacts therein during the short interval involved between the successive openings of the parallel sets of contacts, said arrangement comprising the combination of current-diverting impedance means connected in effective electrical currentdiverting relation with the parallel sets of contacts, and a balancing inductance having a winding with two ends and a center-tap dividing the said winding into two halves with a half thereof included in each of the two parallel contact paths for developing, in series with each of the parallel sets of contacts, an inductive impedance to the flow of current there in, the inductive impedance in the yet uninterrupted parallel contact path opposing the sudden re-establishment of the current of the interrupted parallel contact path during the short interval involved between the successive openings of the parallel sets of contacts in the yet uninterrupted parallel path, thereby preventing the damaging of the contacts, the said center-tap being connected to the load circuit and Ithe said ends of the balancing winding being connected respectively to the two parallel contact paths, thus forming a T-connection to balance out the inductive impedance of the said winding with respect to the load circuit, said current-diverting impedance means comprising capacitance means separated into two parts of substantially the same capacitance value, with one of said parts connected in shunt with the interrupting set of contacts of one parallel path and with the other of said parts connected in shunt with the interrupting set of contacts of the other parallel path, the capacitance of each of said parts permitting the current which flows therein during the short interval involved between the successive openings of the parallel sets, of contacts to be of substantially the same value as the current which flowed through the associated parallel path prior to the opening of the interrupting set of contacts therein.

8. In an electrical system including a load circuit and having a circuit interrupting device therefor with at least two parallel sets of interrupting contacts substantially simultaneously operated for jointly supplying a current through a plurality of parallel contact paths to the load circuit; the arrangement for preventing the current which is interrupted in an interrupted parallel contact path incident to slight variations in the breaking of the plurality of sets of contacts from suddenly re-establishing itself in a yet uninterrupted parallel contact path and increasing the burden on the set of contacts therein during the short interval involved between the successive openings of the parallel sets of contacts, said arrangement comprising the combination of current-diverting impedance means connected in effective electrical current-diverting relation with the parallel sets of contacts, and a balancing inductance having a winding with two ends and a center-tap dividing the said winding into two halves with a half thereof included in each of the two parallel contact paths for developing, in series with each o1' the parallel sets of contacts, an inductive impedance to the now of current therein, the inductive impedance in the yet uninterrupted parallel contact path opposing the sudden re-establishment of the current of the interrupted parallel contact path during the short interval involved between the successive openings of the parallel sets of contacts in'the yet uninterrupted parallel path, thereby preventing the damaging of the contacts, the said center-tap being connected to the load circuit and the said ends of the balancing winding being connected respectively to the two parallel contact paths, thus forming a T-connection to balance out the inductive impedance of the said winding with respect to the load circuit, said current-diverting impedance means being separated into two parts of substantially the same impedance value, with one of said parts connected in shunt with the interrupting set of contacts of one parallel path and with the other of said parts connected in shunt with the Iinterrupting set of contacts of the other parallel path, the impedance of each of said parts permitting the current which flows therein during the short interval involved between the successive openings of the parallel sets of contacts to be substantially one-half the value of the current which flowed through the associated parallel path prior to the opening of the interrupting set of contacts therein.

9. In an electrical system including a load circuit and having a circuit interrupting device therefor with at least two parallel sets of interrupting contacts substantially simultaneously operated for jointly supplying a current through a plurality of parallel contact paths to the load circuit; the arrangement for preventing the current which is interrupted in an interrupted parallel contact path incident to slight variations in the breaking of the plurality of sets of contacts from suddenly re-establishing itself in a yet uninterrupted parallel contact path and increasing the burden on the set of contacts therein during the short interval involved between the successive openings of the parallel sets oi contacts, said arrangement comprising the combination of current-diverting impedance means connected in efective electrical current-diverting relation with the parallel sets of contacts, and a balancing inductance having a winding with two ends and a center-tap dividing the said Winding into two halves with a half thereof included in each of the two parallel contact paths for developing, in series with each of the parallel sets of contacts, an inductive impedance to the llow of current therein, the inductive impedance in the yet uninterrupted parallel contact path opposing the sudden re-establishment of the current of the interrupted parallel contact path during the short interval involved between the successive openings of the parallel sets of contacts in the yet uninterrupted parallel path, thereby preventing thedamaging of the contacts, the said ccnter-tap being connected to the load circuit and the said ends of the balancing winding being connected respectively to the two parallel contact allel path and with the other of said parts connected in shunt with the interrupting set of contacts of the other parallel path, each of said impedance parts comprising the combination of resistance means and capacitance means which permits the current which flows therein during the short interval involved between the successive openings oi' the parallel sets of contacts to be substantially one-half the value of the current which flowed through the associated parallel path prior to the opening of the interrupting set of contacts therein.

10. In an electrical system including a load circuit and having a circuit interrupting device therefor With at least two parallel sets of interrupting contacts substantially simultaneously operated for jointly supplying a. current through a plurality of parallel contact pathsto the load circuit; the arrangement for preventing the current which is interrupted in an interrupted parallel contact path incident to slight variations in the breaking of the plurality of sets of contacts from suddenly re-establishing itself in a yet uninterrupted parallel contact path and increasing the burden on the set of contacts therein during the short interval involved between the successive openings of the parallel sets of contacts, said arrangement comprising the combination of current-diverting impedance means connected in eifective electrical current-diverting relation with the parallel sets of contacts, and a balancing inductance having a winding with two ends and a center-tap dividing the said winding into two halves with a half thereof included in each of the two parallel contact paths for developing, in series with each of the parallel sets of contacts, an inductive impedance to the flow of current therein, the inductive impedance in the yet uninterrupted parallel contact path opposing the sudden re-establishment of the current of the interrupted parallel contact path during-the short interval involved between the successive openings of the parallel sets of contacts in the yet uninterrupted parallel path, thereby preventing the damaging of the contacts, the said center-tap being connected to the load circuit and the said ends of the balancing winding being co-nnected respectively to the two parallel contact paths, thus forming a T-connection to balance out the inductive impedance of the said winding with respect to the load circuit, said current-diverting impedance means being connected across the parallel contact paths and in shunt With the balancing inductance to form a current-diverting loop circuit.

11. In an electrical system including a load circuit and having a circuit interrupting device therefor with at least two parallel sets of interrupting contacts substantially simultaneously operated for jointly supplying a current through a plurality of parallel contact paths to the load circuit; the arrangement for preventing the current which is interrupted in an interrupted par-` allel Contact path incident to slight variations in the breaking of the plurality of sets of contacts from suddenly re-establishing itself in a yet uninterrupted parallel contact path and increasing the burden on the set of contacts therein during the short interval involved between the successive openings of the parallel sets of contacts, said arrangement lcomprising the combination of current-diverting impedance means connected in effective electrical current-diverting relation with the parallel sets of contacts, and a balancing inductance having a winding with two ends and a center-tap dividing the said winding into two halves with a half thereof included in each of the two parallel contact paths for developing, in series with each of the parallel sets of contacts, an inductive impedance to the flow of current therein, the inductive impedance in the yet uninterrupted parallel contact path opposing the sudden re-establishment of the current of the interrupted parallel contact path duringl the short interval involved between the successive openings of the parallel sets of contacts in the yet uninterrupted parallel path, thereby preventing the damaging of the contacts, the said center-tap being connected to the load circuit and the said ends of the balancing winding being connected respectively to the two parallel contact paths, thus forming a T-connection to balance out the inductive impedance of the said winding with respect to the load circuit, said current-diverting impedance means being connected across the parallel contact paths and in shunt with the balancing inductance to form a current-diverting loop circuit, said current-diverting impedance means having a value substantially four times the value of the impedance of the load circuit.

12. In an ignition system including a load circuit and having a circuit interrupting device therefor With at least two parallel sets of interrupting contacts substantially simultaneously operated for jointly supplying a current through a plurality of parallel contact paths to the load circuit; the arrangement for preventing the current which is interrupted in an interrupted parallel contact path incidentl to slight variations in the breaking of the plurality of sets of contacts from suddenly re-establishing itself in a yet uninterrupted parallel contact path Aand increasing the burden on the set of contacts therein during the short interval involved between the successive openings of the parallel sets of contacts, said arrangement comprising the combination of current-diverting capacitance means connected across the contacts of each set of contacts, and a balancing inductance having a winding with two ends and a center-tap dividing the said winding into two halves with a half thereof included in each of the two parallel contact paths for developing, in series with each of the parallel sets of contacts, an inductive impedance to the flow of current therein, the inductive impedance in the yet uninterrupted parallel contact path opposing the sudden re-establishment of the current of the interrupted parallel contact path during the short interval involved between the successive openings of the parallel'sets of contacts in the yet uninterrupted parallel path, thereby preventing the damaging of the contacts, the said center-tap being connected to the load circuit and the said ends of the balancing winding being connected respectively to the two parallel contact paths, thus forming a T-connection to balance out the inductive impedance of the said winding with respect to the load circuit.

13. In a load circuit having two parallel sets of interrupting contacts, current-diverting means connected in effective current-diverting relation with the two Sets of contacts, and balancing inductance means having a balancing winding with a center-tap included in the load circuit and dividing the said winding into two halves with a half thereof included respectively in series with each of the two sets of parallel contacts.

14. In an interrupter system having interrupting means for interrupting a plurality of parallel interrupting paths, said parallel paths being substantially simultaneously interrupted by the interrupting means for jointly interrupting the current in the system, current-diverting means connected in effective current-diverting relation with the parallel paths, and balancing inductance means having a plurality of inductance windings, each inductance winding being respectively connected in series with the interrupting parallel paths for developing, in series with each of the interrupting parallel paths, an inductive impedance to the flow of the current therein, said plurality of inductance windings having tap connection means to establish opposed nuxes therein to minimize the inductive impedance to the now of the current in the system.

15. In an interrupter system having interrupting means for interrupting two parallel interrupting paths, said parallel paths being substantially simultaneously interrupted `by the interrupting means for jointly interrupting the current in the system, current-diverting means connected in effective current-diverting relation with the said parallel paths, and balancing inductance means having a balancing Winding with a center-tap connection dividing the said balancing winding into two halves with a half thereof connected in series with each 0f the interrupting parallel paths for developing, in series with each of the said interrupting parallel paths an inductive impedance to the flow of the current therein.

16. In an interrupter system having interrupting means for interrupting a plurality of interrupting paths, said interrupting paths being substantially simultaneously interrupted by the interrupting -means for jointly interrupting the current in the system; the arrangement for preventing the current which is interrupted in an interrupted parallel path incident to slight variations in the interruption of the parallel paths from suddenly re-establishing itself in a yet uninterrupted parallel path and increasing the burden of the said yet uninterrupted parallel path during the short interval involved between successive interruptions of the parallel paths, said arrangement comprising current-diverting means connected in eiective current-diverting relation with the interrupting parallel paths, and balancing inductance means having a plurality of inductance windings, each inductance winding being respectively connected in series with the interrupting parallel paths for developing in series with each of the interrupting parallel paths, an inductive impedance to the iiow of the current therein, the inductive impedance in the yet uninterrupted parallel path in combination with the current-diverting means opposing the sudden re-establishment of the current of an interrupted parallel path during the short interv-al 17. In an interrupter system having interrupting means for interrupting a plurality of interrupting paths, said interrupting paths being substantially simultaneously interrupted by the interrupting means for jointly interrupting the current in the system; the arrangement for preventing the current which is interrupted in an interrupted parallel path incident to slight variations in the interruption of the parallel paths from suddenly re-establishing itself in a yet uninterrupted parallel path and increasing the burden of the said yet uninterrupted parallel path during the short interval involved between successive interruptions of the parallel paths, said arrangement comprising current-diverting means connected in eiective currentdiverting relation with the interrupting parallel paths, and balancing inductance means having a plurality of inductance windings, each inductance winding being respectively connected in series with the interrupting parallel paths for developing in series with each of the interrupting parallel paths, an inductive impedance to the flow of the current therein, the inductive impedance in the yet uninterrupted parallel path in combination with the current-diverting means opposing the sudden re-establishment o1' the current of an interrupted parallel path during the short interval involved between the successive interruptions of the parallel paths in the yet uninterrupted path, thereby preventing the damaging of the interrupting means, each group of inductance windings having tap connection means to establish opposing fluxes in the windings to minimize the inductive impedance to the flow of the current in the system, said current-diverting means being connected across the parallel paths and in shunt with the inductance windings.

18. In an interrupter system having interrupting means for interrupting a plurality of interrupting paths, said interrupting paths being substantially simultaneously interrupted by the interrupting means for jointly interrupting the current in the system; the arrangement for preventing the currentwhich is interrupted in an interrupted parallel path incident to slight variations in the interruption of the parallel paths from suddenly re-establishing itself in a yet uninterrupted parallel path and increasing the burden of the said yet uninterrupted parallel path during the short interval involved between successive interruptions or the parallel paths, said arrangement comprising current-diverting means connected in eective current-diverting relation with the interrupting parallel paths. and balancing inductance means having a plurality of inductance windings, each inductance winding being respectively connected in series with the interrupting parallel paths for developing in series with each of the interrupting parallel paths, an inductive impedance to the ow of the current therein, the inductive impedance in the yet uninterrupted parallel path in combination with the current-diverting means opposing the sudden re-establishment of the current in an interrupted parallel path during the short interval involved between the successive interruptions of the parallel paths in the yet unin terrupted path, thereby preventing the damaging of the interrupting means, each group of inductance windings having tap connection means to establish opposing iluxes in the windings to minimize the inductive impedance to the flow of the current in the system, said current-diverting means comprising a plurality of parts, with a part connected in shunt with the interrupting means of each parallel path and in series with the inductance windings.

19. In an ignition system having interrupting means for interrupting a plurality of interrupting paths, said interrupting paths being substantially simultaneously interrupted by the interrupting means for jointly interrupting the current in the system; the arrangement for preventing the current which is interrupted in an interrupted parallel path incident to slight variations in the interruption of the parallel paths from suddenly re-establishing itself in a yet uninterrupted parallel path and increasing the burden of the said yet uninterrupted parallel path during the short interval involved between successive interruptions of the parallel paths, said arrangement comprising current-diverting means connected in effective current-diverting relation with the interrupting parallel paths, and balancing inductance means having a plurality ot inductance windings, each inductance winding being respectively connected in series with the' interrupting parallel paths for developing in series with each of the interrupting parallel paths, an inductive impedance to the ilow of the current therein, the inductive impedance in the yet uninterrupted parallel paths in combination with the current-diverting means opposing the sudden re-establishment of the current of an interrupted parallel path during the short interval involved between the successive interruptions or the parallel paths in the yet uninterrupted path, thereby preventing the damaging of the inten'upting means, each group o! inductance windings having tap connection means to establish opposing nuxes in the windings to minimize the inductive impedance to the flow of the current in the system.

HAROLD J. BROWN. 

